5 // return f(l.hd) : map(f, l.tl);
13 // return foldr(f, f(acc, l.hd), l.tl);
22 // return filter(f, l.tl);
24 // return l.hd : filter(f, l.tl);
33 // return x : intList(x-1);
54 // print("faculty of 5 is: ", foldr(\x y->x*y, 1, intList(5)));
55 // print("sum of 1..5 is: ", foldr(\x y->x+y, 0, intList(5)));
56 // print("filter evens from 0..12 is: ");
57 // print("sum of 0..12 but only the evens: ",
58 // foldr(\x y->x+y, 0, filter(\x->x%2 == 0, intList(12))));